The present invention relates to a three-dimensional plastic vessel that has excellent in gas-impermeability and suitable for packaging and other purposes, and relates to a process for coating a transparent silicon compound film that is excellent in gas-impermeability on a vessel made of a plastic material.
Packaging materials are required to prevent permeation or transmission of gas for protection and preservation of the contents. Many attempts have been made to achieve this requirement. For example, efforts for providing inorganic layers such as silicon oxide or aluminum oxide, lamination of gas-impermeable resinous layers such as polyvinylidene chloride, and lamination of metallic aluminum foil have been made.
In addition, Japanese Laid-Open Patent No. 3-183759/1991 discloses a film layer, in which an organic thin layer is formed as a coating to a plastic film by applying the synthetic resin the same as the plastic by means of vacuum deposition or sputtering, and an inorganic material is deposited in vacuum thereon to form a mixed layer of the organic and inorganic layers on which further inorganic layer is formed. Since such plastic is quite different from the inorganic layer of the coating layer and has poor affinity, the intermediate blended layer of the synthetic resin and the inorganic material is provided; however, the presence of the synthetic resin surface in the blended layer in addition to the inorganic material does not give the improvement of the fixation of the inorganic material as expected.
Furthermore, the two-step vapor deposition of the synthetic resin and inorganic material cannot be applicable to molded products for example except sheet-form materials.
Furthermore, the molecular weight of the synthetic resin is decreased by the vapor deposition; thereby, the vessel comprising this plastic material has poor processability.
The present inventor previously filed patent applications for Japanese Laid-Open Patent No. 5-345385/1993 and Japanese Patent Application No. 5-224903/1993. These inventions are quite different from conventional packaging materials overcoming defects of conventional packaging materials. However, they are not satisfactory to a certain extent in formation of coated films of ultraprecise uniform thickness although coated films of uniform thickness can be formed for three-dimensional vessels. Ultraprecise uniform thickness is required for special uses such as for packaging special drugs.
The object of the present invention is to form a film of ultraprecise thickness in which the difference of the film thickness is not more than 200 xc3x85 for example, overcomes the problem of nonuniformity in film thickness as mentioned above, and improves the gas-impermeability significantly.